Calcium channel inhibitors (CCI's) are thought to affect calcium flux through membrane bound channels as their major site of action. There are reports of clinical trials involving over 150 patients suggesting that CCI's also have beneficial effects in neuropsychiatric disorders. There are four major subclasses of CCI's, where each appears to have unique combinations of biochemical and behavioral properties. Additional studies have suggested a complex interaction between dopamine receptor function and calcium channels. We have completed a study of the clinical effects of verapamil in a schizophrenic population where trends toward improvement did not reach statistical significance. We are proceeding with the planned protocol to examine the effects of nifedipine in a similar cohort. Differente results are to be expected on the basis of preliminary work where nifedipine differed from verapamil its effects on animal behavior in models of dopaminergic activity.